Aqueous carbon black formulations for ink jet

ABSTRACT

Finely divided solids are highly suitable for use as stabilizers for pyrocarbonic acid diesters, it being possible to use the mixtures obtained in this manner for preserving industrial materials and foodstuff.

The present invention relates to the use of finely divided solids asstabilizers for pyrocarbonic acid diesters, to mixtures comprisingpyrocarbonic acid diesters and finely divided solids and also to the useof these mixture for preserving industrial materials and foodstuff.

Pyrocarbonic acid diesters are used, inter alia, for preservingfoodstuff, as components of antimicrobial reagents, for deactivatingenzymes in fermentation processes, or for the synthesis of finechemicals or polymers. Pyrocarbonic acid diesters are used, in addition,for example as catalysts for the oxidation of amines, or for synthesis,for example in the introduction of protecting groups.

It is known that the stability of pyrocarbonic acid diesters can berelatively low at room temperature, and in particular at elevatedtemperature. In particular during purification, for example inpurification by distillation, or during relatively long storage,decomposition of pyrocarbonic acid diesters can therefore occur. Thisdecomposition can impair the quality and purity of the pyrocarbonic aciddiesters. In addition, the decomposition generally proceeds more rapidlythe more impurities are present. High purity and stabilization ofpyrocarbonic acid diesters are therefore highly desirable.

Methods for improving the thermal stability of pyrocarbonic aciddiesters are already known from the prior art. For instance, it isproposed, for example, to stabilize dialkyl pyrocarbonates by addingmetal sulphates (cf. JP-A 48-4016). A disadvantage of this method,however, is that these metal sulphates are sparingly to poorly misciblewith the dialkyl pyrocarbonates.

In addition, it is known to stabilize dialkyl pyrocarbonates by addingboron compounds (cf. JP-A 46-37810). This, however, has inter alia thedisadvantage that these compounds are likewise poorly miscible with thedialkyl pyrocarbonates.

In addition, carbonyl compounds and also heteroanalogous carbonylcompounds have been proposed as additives increasing the storagestability of solutions of dialkyl pyrocarbonates in solvents inert todialkyl pyrocarbonate (cf. DE-A 3231397). However, stabilizing effectscan only be achieved with relatively high percentages of additives.

There was therefore a need for stabilizers suitable for protectingpyrocarbonic acid diesters even more effectively against thermaldecomposition.

Surprisingly, it has now been found that pyrocarbonic acid diesters canbe stabilized very efficiently by adding certain finely divided solids(insoluble in pyrocarbonic acid diesters) against thermal and/orchemical degradation reactions which may occur, for example, duringstorage or distillative purification.

Accordingly, the present invention provides the use of at least onefinely divided solid as an additive for pyrocarbonic acid diesters forstabilizing them against chemical and/or thermal degradation reactions.

The pyrocarbonic acid diesters are preferably compounds of the generalformula (I)

in which

-   R¹ and R² independently of one another represent straight-chain or    branched C₁-C₈-alkyl, cycloalkyl, C₂-C₈-alkenyl, C₂-C₈-alkynyl or    benzyl which is in each case optionally mono- or polysubstituted by    identical or different substituents from the group consisting of    halogen, nitro, cyano, C₁-C₆-alkoxy, dialkylamino; or represent    phenyl which is optionally mono- or polysubstituted by identical or    different substituents from the group consisting of halogen, nitro,    cyano, alkyl, haloalkyl, alkoxy, haloalkoxy, acyl, acyloxy,    alkoxycarbonyl, carboxyl,    preferably-   R¹ and R² independently of one another represent straight-chain or    branched C₁-C₈-alkyl or C₂-C₈-alkenyl or benzyl, particularly    preferably-   R¹ and R² independently of one another represent straight-chain or    branched C₁-C₅-alkyl or C₃-alkenyl or benzyl,    and very particularly preferably-   R¹ and R² independently of one another represent methyl, ethyl,    isopropyl, tert-butyl, tert-amyl, allyl or benzyl.

The stabilizer additives to be used according to the invention arefinely divided solids which are virtually insoluble in pyrocarbonic aciddiesters. The solids are preferably inorganic compounds or mixturesthereof whose solubility in pyrocarbonic acid diesters at roomtemperature is less than 1 ppm and particularly preferably less than 0.1ppm.

The particle size, determined by screening, of the finely divided solidsto be used according to the invention is preferably in the range of ≦200μm. Particularly preferably, the particle size, determined by screening,is in the range of ≦80 μm and very particularly preferably in the rangeof ≦32 m.

Particles of suitable dimensions can be obtained by grinding the solidto the desired particle size followed by fractional screening usingscreens having the corresponding mesh sizes of ≦200, 80 or ≦32 μm. Thescreens are, for example, analytical screens from Retsch (according toISO 565/DIN 3310-1).

The finely divided solids to be used according to the invention arepreferably metal oxides, metal sulphides and Lewis acids which arepresent in the solid state of aggregation at room temperature.

Preferred metal oxides are compounds or mixtures thereof of the generalformula M₂O, MO, M₂O₃, MO₂, M₂O₅, MO₃, M₂O₇, MO₄ or double oxides suchas, for example, M₃O₄, where M is in each case preferably a metal ion orsemimetal ion from the group of the first to fourth main group or thetransition group or the lanthanoid group of the Periodic Table of theElements, particularly preferably a metal ion or semimetal ion of thethird main group or the transition group or the lanthanoid group of thePeriodic Table of the Elements. Very particular preference is given, forexample, to B₂O₃.

Preferred metal sulphides are compounds of the general formula M₂S, MS,M₂S₃ or MS₂, where M is as defined above.

Preferred Lewis acids are, for example, boric acid, metaboric acid,lanthanum triflate, ZrCl₄, HfCl₄, TaCl₅, WCl₆, NbCl₅ or YCl₃.

The general, preferred and particularly preferred solids mentioned canbe ground to the desired particle size using instruments usuallyemployed for comminuting, for example in a ball mill or in a mortar.

After comminution, the finely divided solids can be employed directly,or they can be presuspended in a suitable manner. Suitable forsuspending are, for example, pyrocarbonic acid diesters, alcohols orwater.

The finely divided solids can also be employed immobilized on surfaces.Matrices suitable for this purpose are, for example, activated carbon orsilicic carrier materials. Also suitable as matrices for theimmobilization are organic polymers, such as, for example, polyethylene,polypropylene, polyesters, polystyrene or polycarbonate.

The finely divided solids mentioned are generally employed in an amountof from 0.01 to 100 000 ppm, preferably in an amount of from 0.1 to 10000 ppm, particularly preferably in an amount of from 0.1 to 3000 ppm,very particularly preferably in an amount of from 0.1 to 1000 ppm, basedon the pyrocarbonic acid diester or its mixture.

By the use according to the invention, it is possible to stabilizepyrocarbonic acid diesters in a general manner against thermal andchemical degradation reactions. Such degradation reactions occur, forexample, on storage.

The pyrocarbonic acid diesters stabilized according to the invention aredistinguished by improved storage stability. Thus, the pyrocarbonic aciddiesters stabilized in this manner can be stored at room temperatureover a period of several months without a decomposition of thepyrocarbonic acid diesters being observed.

The present invention furthermore provides mixtures comprising one ormore pyrocarbonic acid diesters of the formula (I) shown above and oneor more of the finely divided solids described above in a general and apreferred manner in an amount of generally from 0.01 to 100 000 ppm,preferably from 0.1 to 10 000 ppm, particularly preferably from 0.1 to3000 ppm and very particularly preferably from 0.1 to 1000 ppm, based onthe pyrocarbonic acid diester or its mixture.

Very particular preference is given to mixtures comprisingdimethylpyrocarbonate and/or diethyl pyrocarbonate and B₂O₃ of aparticle size, determined by screening, of ≦32 μm.

The mixtures according to the invention can be stored over a period ofseveral months without a decomposition of the pyrocarbonic acid diesterscontained therein occurring.

The mixtures according to the invention are highly suitable forprotecting and preserving industrial materials and foodstuff and inparticular beverages against attack and/or decomposition bymicroorganisms, such as, for example, bacteria, fungi or yeasts.

The present invention likewise relates to the use of the mixturesaccording to the invention for protecting industrial materials and forpreserving foodstuff and beverages.

The pyrocarbonic acid diesters stabilized according to the invention areoutstandingly suitable, for example, as cold disinfectants for still orcarbonated drinks such as soft drinks, vitamin drinks, fruit juicedrinks, tea drinks, alcoholic or dealcoholized wine drinks, fruitpunches or some beers. Customarily, for this the pyrocarbonic aciddiesters are added in amounts between 10 and 250 ppm close in time topackaging the beverages. Admixture to the beverages is performed usingspecial metering pumps. The pyrocarbonic acid diesters act so as tocontrol a number of microorganisms such as fermentative yeasts, mouldsor fermentative bacteria. Examples which may be mentioned here are, forinstance, Saccharomyces cervisiae, Mycoderma, Brettanomyces spp,Lactobacillus brevis, Lactobacillus buchneri and many others.

The pyrocarbonic acid diesters stabilized according to the invention arefurthermore also suitable for protecting industrial materials againstattack and destruction by unwanted microorganisms.

In the present context, industrial materials are to be understood asmeaning non-living materials which have been prepared for use inindustry. The industrial materials are, for example, adhesives, sizes,paper and board, textiles, leather, wood, timber products, woodcomposites, paints and plastic articles, cooling lubricants and othermaterials which can be colonized or destroyed by microorganisms.Furthermore, in the context of the present invention, industrialmaterials are also to be understood as meaning parts of productionplants, for example cooling-water circuits, which may be impaired by theproliferation of microorganisms. Industrial materials which arepreferably protected are adhesives, sizes, paper and board, leather,wood, timber products, wood composites, paints, plastic articles,cooling lubricants and heat-transfer liquids.

The pyrocarbonic acid diesters of the general formula (I) stabilizedaccording to the invention are particularly suitable for protectingwood, timber products, wood composites, plastic, cooling lubricants,aqueous and/or solvent-comprising organic or inorganic dispersions andcoating systems, such as paints, varnishes or plaster, againstcolonization by microorganisms.

Microorganisms capable of degrading or changing the industrial materialswhich may be mentioned are, for example, bacteria, fungi, yeasts, algaeand slime organisms. The pyrocarbonic acid diesters stabilized accordingto the invention preferably act against yeasts, bacteria and fungi.

Mention may be made, for example, of microorganisms of the followinggenera:

Acetobacter pasteurianus,Aspergillus, such as Aspergillus niger,Candida kruseiChaetomium, such as Chaetomium globosum,Escherichia, such as Escherichia coli,Penicillium, such as Penicillium glaucum,Pseudomonas, such as Pseudomonas aeruginosa,Rhodotorula such as Rhodotorula rubraSaccharomyces such as Saccharomyces cervisiaeStaphylococcus, such as Staphylococcus aureus.

Thermal degradation reactions of pyrocarbonic acid diesters also occur,furthermore, in particular in the distillation of pyrocarbonic aciddiesters as carried out, for example, in the context of the preparationprocess for pyrocarbonic acid diesters. By means of the inventive use offinely divided stabilizers it is possible to distil pyrocarbonic aciddiesters with lower losses and in higher purity.

Accordingly, the present invention further relates to a process for thedistillative purification of pyrocarbonic acid diesters, by adding oneor more pyrocarbonic acid diesters of the formula (I) specified above toone or more of the finely divided solids mentioned above as beingpreferred and particularly preferred, in general in an amount of from0.01 to 100 000 ppm, preferably in an amount of from 0.1 to 10 000 ppm,in each case based on the pyrocarbonic acid diester or its mixture, andsubsequently distilling the mixture at a pressure of from 5 to 100 mbar,preferably from 10 to 50 mbar, and a temperature between 30 and 120° C.,preferably between 40 and 90° C. Distillation columns customary inindustry are suitable for the distillation.

The yields of pyrocarbonic acid diester in the distillation are usually>99%.

The examples below serve to illustrate the present invention without,however, restricting its subject-matter thereto.

EXAMPLES

Corresponding to the data in Tables 1-3, in each case defined amounts ofa defined high-purity pyrocarbonic acid diester and the respectivestated solid additives were weighed in a 10 ml round-bottomed flaskequipped with a magnetic stirrer. The exact amounts of the additivesused in each case are also given in the tables.

The solids were either used directly (coarse) or finely groundbeforehand using a mortar (fine). In these experiments, the achievedreduction in particle size was not determined any further. However, forthe accurate determination of the particle size, screens having definedmesh sizes (32 μm, 80 μm, 200 μm) were used. Starting with the smallestmesh size, it was thus possible to screen particle sizes as indicated inTable 1 from the stabilizing agent finely comminuted beforehand.

The round-bottomed flask was tightly closed using a septum. In thisseptum was situated an orifice in which a Teflon tube was attached,which was passed into a vertical silicone-oil-filled 50 ml burettecalibrated to 0.1 ml. On the scale of the burette, the amount of thecarbon dioxide developing as a result of the decomposition of thepyrocarbonic acid diester could be read off. The flask was promptlylowered into a constant temperature oil bath (stirred at 500 rpm) asspecified in Tables 1-3 for the respective experiment. The depth ofimmersion of the flask was 2.0 cm.

After the respective stated time, in general after 1, 2, 5, 10 and 15minutes, the gas volume was read off. The gas volume is a measure of thedegree of decomposition of the pyrocarbonic acid diester. It thusinversely reflects the degree of stabilization by the additives tested.

The results are shown in the appended tables. High-purity pyrocarbonicacid diester, in the observed time, released little carbon dioxide, buteven contact with small amounts of silica gel drastically accelerateddecomposition. The more finely divided the stabilizer, the higher itsstabilizing effect.

TABLE 1 Diethyl dicarbonate, 5000 ppm addition of solid stabilizerTemperature [° C.] 130 130 130 130 130 130 Diethyl dicarbonate 1 1 1 1 11 quantity [g] Addition without silica gel silica gel silica gel silicagel silica gel Quantity [mg] 10 10 10 10 10 Addition solid withoutwithout B₂O₃ B₂O₃ B₂O₃ B₂O₃ Quantity [mg] 5 5 5 5 Particle size [μm] <32μm 32-80 μm 80-200 μm >1000 μm Evolution of gas [ml] Minutes 1 0.5 2.50.9 1.9 2.4 1.7 Minutes 2 1.0 7.2 2.0 3.8 4.3 5.1 Minutes 5 1.2 28.9 3.16.0 7.4 11.1 Minutes 10 1.3 46.3 4.9 8.1 10.0 22.3 Minutes 15 1.3 50.06.9 10.1 12.1 32.0

TABLE 2 Dimethyl dicarbonate, 6670 ppm addition of solid stabilizerTemperature [° C.] 100 100 100 100 100 100 Dimethyl dicarbonate 3 3 3 33 3 quantity [g] Addition without silica gel silica gel silica gelsilica gel silica gel Quantity [mg] 10 10 10 10 10 Addition solidwithout without Boric acid Boric acid B₂O₃ B₂O₃ coarse fine coarse fineQuantity [mg] 20 20 20 20 Evolution of gas [ml] Minutes 1 0.1 1.0 0.90.4 0.8 0.7 Minutes 2 0.2 3.4 3.3 1.8 2.8 2.2 Minutes 5 0.6 20.3 7.7 3.97.3 4.9 Minutes 10 0.8 46.1 10.0 5.1 12.7 6.4 Minutes 15 1.3 50.0 10.96.1 15.8 7.2

TABLE 3 Dimethyl dicarbonate, 1670 ppm addition of solid stabilizerTemperature [° C.] 100 100 100 100 Dimethyl dicarbonate quantity [g] 3 33 3 Addition Quantity [mg] silica gel silica gel silica gel without 1010 10 Addition solid Quantity [mg] B₂O₃ B₂O₃ coarse fine Evolution ofgas [ml] without without 5 5 Minutes 1 0.1 1.0 0.4 0.4 Minutes 2 0.2 3.42.1 1.8 Minutes 5 0.6 20.3 9.8 6.1 Minutes 10 0.8 46.1 22.6 12.6 Minutes15 1.3 50.0 32.9 16.6

1. Use of at least one finely divided solid as additive for pyrocarbonicacid diesters for stabilizing them against chemical and/or thermaldegradation reactions.
 2. Use according to claim 1, characterized inthat the solid is an inorganic compound whose solubility in thepyrocarbonic acid diester at room temperature is less than 1 ppm.
 3. Useaccording to at least one of claims 1 and 2, characterized in that thesolid has a particle size, determined by screening, in the range of ≦200μm.
 4. Use according to at least one of claims 1 to 3, characterized inthat the solid is a metal oxide, metal sulphide or a Lewis acid which ispresent in the solid state of aggregation at room temperature.
 5. Useaccording to at least one of claims 1 to 4, characterized in that thesolid is (i) a metal oxide of the formula M₂O, MO, M₂O₃, MO₂, M₂O₅, MO₃,M₂O₇, MO₄ or a double oxide of the formula M₃O₄, where M is a metal ionor semimetal ion from the group of the first to fourth main group or thetransition group or the lanthanoid group of the Periodic Table of theElements, (ii) a metal sulphide of the formula M₂S, MS, M₂S₃ or MS₂,where M is as defined above, or (iii) a Lewis acid from the groupconsisting of boric acid, metaboric acid, lanthanum triflate, ZrCl₄,HfCl₄, TaCl₅, WCl₆, NbCl₅ and YCl₃.
 6. Use according to at least one ofclaims 1 to 5, characterized in that the dialkyl pyrocarbonates arecompounds of the general formula

in which R¹ and R² independently of one another represent straight-chainor branched C₁-C₈-alkyl, cycloalkyl, C₂-C₈-alkenyl, C₂-C₈-alkynyl orbenzyl which is in each case optionally mono- or polysubstituted byidentical or different substituents from the group consisting ofhalogen, nitro, cyano, C₁-C₆-alkoxy, dialkylamino; or represent phenylwhich is optionally mono- or polysubstituted by identical or differentsubstituents from the group consisting of halogen, nitro, cyano, alkyl,haloalkyl, alkoxy, haloalkoxy, acyl, acyloxy, alkoxycarbonyl, carboxyl.7. Use according to at least one of claims 1 to 6, characterized in thatthe dialkyl pyrocarbonates are dimethylpyrocarbonates or diethylpyrocarbonates.
 8. Use according to at least one of claims 1 to 7,characterized in that the solid or its mixture is employed in an amountof from 0.01 to 100 000 ppm, based on the dialkyl pyrocarbonate or itsmixture.
 9. Use according to at least one of claims 1 to 8,characterized in that the stabilization is against degradation reactionsduring distillation or storage.
 10. Mixtures comprising one or moredialkyl pyrocarbonates of the general formula

in which R¹ and R² independently of one another represent straight-chainor branched C₁-C₈-alkyl, cycloalkyl, C₂-C₈-alkenyl, C₂-C₈-alkynyl orbenzyl which is in each case optionally mono- or polysubstituted byidentical or different substituents from the group consisting ofhalogen, nitro, cyano, C₁-C₆-alkoxy, dialkylamino; or represent phenylwhich is optionally mono- or polysubstituted by identical or differentsubstituents from the group consisting of halogen, nitro, cyano, alkyl,haloalkyl, alkoxy, haloalkoxy, acyl, acyloxy, alkoxycarbonyl, carboxyl,and one or more finely divided solids in an amount of from 0.01 to 100000 ppm, based on the dialkyl pyrocarbonate or its mixtures.
 11. Mixtureaccording to claim 10, characterized in that the solids are inorganiccompounds whose solubility in the pyrocarbonic acid diester or itsmixture at room temperature is less than 1 ppm.
 12. Mixture according toat least one of claims 10 and 11, characterized in that the solids havea particle size, determined by screening, in the range of ≦200 μm. 13.Mixture according to at least one of claims 10 to 12, characterized inthat the solids are (i) metal oxides of the formula M₂O, MO, M₂O₃, MO₂,M₂O₅, MO₃, M₂O₇, MO₄ or double oxides of the formula M₃O₄, where M is ametal ion or semimetal ion from the group of the first to fourth maingroup or the transition group or the lanthanoid group of the PeriodicTable of the Elements, (ii) metal sulphides of the formula M₂S, MS, M₂S₃or MS₂, where M is as defined above, or (iii) Lewis acids from the groupconsisting of boric acid, metaboric acid, lanthanum triflate, ZrCl₄,HfCl₄, TaCl₅, WCl₆, NbCl₅ and YCl₃.
 14. Mixture according to at leastone of claims 10 to 13, characterized in that they comprise at least onecompound from the group consisting of dimethylpyrocarbonate and diethylpyrocarbonate and B₂O₃ having a particle size, determined by screening,of ≦32 μm.
 15. Use of a mixture according to at least one of claims 10to 14 for protecting and preserving industrial materials, foodstuff andbeverages.
 16. Process for the distillative purification of dialkylpyrocarbonates, characterized in that one or more dialkyl pyrocarbonatesof the general formula

in which R¹ and R² independently of one another represent straight-chainor branched C₁-C₈-alkyl, cycloalkyl, C₂-C₈-alkenyl, C₂-C₈-alkynyl orbenzyl which is in each case optionally mono- or polysubstituted byidentical or different substituents from the group consisting ofhalogen, nitro, cyano, C₁-C₆-alkoxy, dialkylamino; or represent phenylwhich is optionally mono- or polysubstituted by identical or differentsubstituents from the group consisting of halogen, nitro, cyano, alkyl,haloalkyl, alkoxy, haloalkoxy, acyl, acyloxy, alkoxycarbonyl, carboxyl,is/are admixed with one or more finely divided solids in an amount offrom 0.01 to 100 000 ppm, based on the dialkyl pyrocarbonate or itsmixture, and the mixture is then distilled at a pressure of from 5 to100 mbar and a temperature between 30 and 120° C.
 17. Process accordingto claim 16, characterized in that the solids are (i) metal oxides ofthe formula M₂O, MO, M₂O₃, MO₂, M₂O₅, MO₃, M₂O₇, MO₄ or double oxides ofthe formula M₃O₄, where M is a metal ion or semimetal ion from the groupof the first to fourth main group or the transition group or thelanthanoid group of the Periodic Table of the Elements, (ii) metalsulphides of the formula M₂S, MS, M₂S₃ or MS₂, where M is as definedabove, or (iii) Lewis acids from the group consisting of boric acid,metaboric acid, lanthanum triflate, ZrCl₄, HfCl₄, TaCl₅, WCl₆, NbCl₅ andYCl₃ which have a particle size, determined by screening, in the rangeof ≦200 μm.